Alloy steels for use at elevated temperatures



Patentecl June 1 2, 1951 ALLOY STEELS FOR USE AT ELEVATED TEMPERATURES Henry William Kirkby and Charles Sykes, Sheffield, England, assignors to Thos. Firth & John Brown Limited, Sheflield, England, a British comp any No Drawing. Application April 14, 1950, Serial No. 156,044. In Great Britain August 23, 1949 This invention relates to alloy steels for use at elevated temperatures.

To provide alloys having a high creep resistance at temperatures up to 800 C. the following range of composition has been proposed (see British specification No. 577,892)

Carbon, up'to 1.5% I Nickel, 15.0 to 25% Chromium, 12.0 to 20.0% Molybdenum, 2.0 to 6.0% Copper, 2.0 to 6.0% Titanium, 0.25 to 2.0% Iron, remainder The above alloy may also contain silicon up to 2%, manganese up to 2% and vanadium up to 1 The addition of cobalt to the above alloys, the cobalt and nickel proportions being respectively 7 to 40% and 25 to l5%for the purpose of improving further the creep resistance propertieshas also been proposed (see British specification No. 616,207), and in such alloys containing cobalt as proposed the substitution of columbium for the whole or part of the titanium content of the alloy has also been suggested.

A further prior proposal in connection with alloys resistant to creep relates to compositions embodying a lower range of nickel, together with cobalt 7 to 50% and columbium 0.5 to 2% interchangeable with titanium.

2 Claims. (Cl. 75-125) The elements cobalt and columbium are strategically rare and consequently their use in al- 10y steels presents an economic difficulty. The

present invention seeks to provide an alloy having high creep resistance properties up to at least 700 0. without relying on either cobalt or 00- lumbium for these properties.

Alloys according to this invention lie within the following range of composition:

The preferred range of composition is as follows:

Carbon, 0.15 to 0.30% Silicon, 0.20 to 0.40%

2 Manganese, 0.20 to 1.0% Chromium, 13.5 to 15.0% Nickel, 8.0 to 11.0% Molybdenum, 1.75 to 2 .25% Copper, 2.0 to 2.75% Tungsten, 0-2.0% Titanium, 0.50 to 1.0% Iron, substantial remainder In the present alloys importance is attached to the low nickel range of proportions and to the inclusion in the alloy of up to 3% of tungsten.

An alloy within the above preferred range of composition, after suitable heat treatment of generally known character, gave the following results of stress to rupture tests:

Stress (tons/ Hours to 2 52-2 fracture The above results compare favourably with known alloys containin considerable proportions of cobalt with or without columbium in addition. Moreover alloys according to the invention are superior to the previously proposed alloys (British specification No. 577,892)already referred tocontaining no cobalt or columbium, as is demonstrated by the following results of comparative stress-rupture tests:

Temp, Stress, Time (hours O. tons/sq. in. to fracture) British Specification No. 650 18 38 577,892 12 Present Application $88 3 denum 2 to 3%, tungsten in efiective proportion up to 3%, copper 1 to 4%, titanium 0.25 to 1%, and balance substantially iron with residual impurities in ordinary amounts.

2. An alloy steel having high creep resistance properties as indicated herein at temperatures up to at least 700 C. and having a composition characterised by the absence of cobalt and columbium and by the presenceas essential constituents of carbon 0.15 to 0.3%, silicon 0.2 to 0.4%, manganese 0.2 to 1%,..chromium 13.5 to 15%, nickel 8 to 11%, molybdenumlflE tom-25%, copper 2 to 2.75%, tungstenin efiective propor- 4 tion 111) to 2%, titanium 0.5 to 1%, and iron the substantial remainder.

HENRY WILLIAM KIRKBY. CHARLES SYKES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,402,814 Hatfield June 25, 1946 2,447; 89'l Clarke Aug. 24, 1948 

1. AN ALLOY STEEL HAVING HIGH CREEP RESISTANCE PROPERTIES AS INDICATED HEREIN AT TEMPERATURES UP TO AT LEAST 700* C. AND HAVING A COMPOSITION CHARACTERISED BY THE ABSENCE OF COBALT AND COLUMBIUM AND BY THE PRESENCE AS ESSENTIAL CONSTITUENTS OF CARBON IN EFFECTIVE PROPORTION UP TO 0.4%, SILICON IN EFFECTIVE PROPORTION UP TO 1%, MANGANESE IN EFFECTIVE PROPORTION UP TO 3%, CHROMIUM 9 TO 17%, NICKEL 7 TO 12%, MOLYBDENUM 2 TO 3%, TUNGSTEN IN EFFECTIVE PROPORTION UP TO 3%, COPPER 1 TO 4%, TITANIUM 0.25 TO 1%, AND BALANCE SUBSTANTIALLY IRON WITH RESIDUAL IMPURITIES IN ORDINARY AMOUNTS. 